Attitudes toward Vaccination for Pandemic H1N1 and Seasonal Influenza in Patients with Hematologic Malignancies
Of the 129 patients surveyed, 85 (66%) reported that they had received the H1N1 pandemic influenza vaccine during the 2009–2010 influenza season. Fifty-seven percent had received the seasonal influenza vaccine, and 50% had received both the seasonal and the H1N1 vaccines. Of the 44 patients who did not receive the H1N1 vaccine, only three planned to receive it. Eight of the 56 patients not vaccinated with the seasonal influenza vaccine planned to receive it.
There were no significant differences in mean age, percentage of patients over 65 years old, gender, or chemotherapy status between patients who received the H1N1 vaccine and those who declined it (Table 1). The mean age of patients who received the seasonal influenza vaccine was significantly higher than that of those who did not (67.8 ±12.1 vs. 56.1 ± 15.5 years, P < 0.0001), and a significantly higher percentage of patients in the vaccinated group were over the age of 65 (67% vs. 33%, P < 0.0001).
Patient-reported reasons for not receiving the H1N1 vaccine are shown in Figure 1. The two most common reasons for declining vaccination were beliefs that “the vaccine is dangerous because of lack of testing” (22%) and “I don't believe in vaccination in general” (18%). The belief that vaccination was dangerous or not effective because of the patient's medical condition represented 16% and 12% of responses, respectively. Six percent responded that receiving the vaccine would have been too inconvenient. No patients reported concerns about pain at the injection site as a reason for avoiding vaccination. In the category of “other,” responses fell into four broad categories: “physician advised against vaccination” (8%), “vaccination is unnecessary” (8%), “previous bad experience from vaccine” (4%), and “vaccine will make me sick” (4%).
Discussion
Our study found that 66% of patients being treated for hematological malignancies at a southwestern Ontario cancer center received the H1N1 vaccine during the 2009–2010 influenza season. This was higher than the rate of H1N1 vaccination in the general Canadian population, which was reported as 41%.14 Canadian cancer patients have been previously shown to have higher rates of participation in vaccination programs. In 2005, 64% of Canadians with cancer received the seasonal influenza vaccine compared with 34% of the overall population.13 This trend may be driven in part by the higher average age of patients receiving cancer treatment as adults 65 years of age or older comprised 52% of the respondents in our study.
Worldwide, Canada ranks among the highest countries in vaccination coverage. The United Kingdom reported a vaccination rate of 28.7% during the 2007–2008 influenza season, which was at the time one of the highest in Europe.19 Other European countries, including Germany, Italy, and France, showed vaccination rates similar to that of the United Kingdom. In all of these countries vaccination coverage increased with age. The United States has vaccination rates most similar to those of Canada, estimated at 40% in the overall population and 68% in the population ≥65 years old during the 2009–2010 influenza season.20
Higher vaccination rates have been reported in the elderly compared to younger adult population,[13] and [14] and our findings prove to be consistent with this reported trend. In this study, the group vaccinated with the seasonal influenza vaccine had a mean age of 67.8 ± 12.1 years compared with the unvaccinated group aged 56.1 ± 15.5 years (P < 0.0001). Interestingly, there was no significant difference in mean age between the vaccinated and unvaccinated groups for the H1N1 pandemic influenza vaccine (P > 0.05). This was not entirely unexpected since public health campaigns during the 2009–2010 influenza season focused on the younger age group due to their increased susceptibility to severe H1N1 disease. Nonetheless, there was a trend toward an increased mean age for those who received the vaccine (64.0 ± 12.5 years) compared to those who did not (60.4 ± 18.4 years), and it is possible that statistical significance was not reached due to the small sample size. Our study reported an alarmingly low 39% vaccination rate for seasonal influenza in cancer patients <65, suggesting that the PHAC's message is not adequately reaching this potentially at-risk group.
Reasons for refusal of vaccination have been well described in previous studies.[16], [17], [18], [21], [22], [23], [24], [25] and [26] We found that the most common reasons for refusal of vaccination by cancer patients were very similar to those reported in healthy individuals. Specifically, concerns about the safety and efficacy of vaccines in general were more common than concerns related to cancer or chemotherapy. The most common reasons for refusal of vaccination were “I think the vaccine will be dangerous for people in general because of lack of testing” (22%) and “I don't believe in vaccination in general” (18%). Despite the publicity, 8% of unvaccinated patients responded that they did not feel that H1N1 influenza was a significant threat. In this study, the belief that the vaccine was dangerous because of lack of testing or a previous medical condition was responsible for 13% of patients not receiving the vaccine. Five percent of patients elected not to be vaccinated because of questions of efficacy. The H1N1 vaccine is an adjuvant with AsO3, which may cause more vaccine reactions, while the seasonal influenza vaccine is not an adjuvant. It is possible that the presence of adjuvant contributed to some patients' safety concerns, though we did not specifically ask if the adjuvant influenced their decision.
Physician advice may have played a significant role in patients' decisions to vaccinate. Eight percent of patients who did not receive the vaccine reported that they were not vaccinated due to advice from a physician. It is our routine institutional policy to recommend vaccination for all cancer patients irrespective of underlying diagnosis or treatment regimen. We do not, however, provide standardized written information to patients or referring physicians, so some patients may have been advised against vaccination by other physicians. Some primary care physicians might not have been familiar with the current PHAC recommendations or the recent literature suggesting the vaccine's potential benefits in this group. Public health campaigns should therefore seek to educate physicians as well as patients regarding the safety and efficacy of the influenza vaccine for cancer patients.
Conclusion
We found that rates of H1N1 and seasonal influenza vaccination in a southwestern Ontario cancer center were higher than those reported for the general population. Nevertheless, despite a large public health education campaign, a significant number of patients declined vaccination due to fear that it would not be safe or effective or due to a belief that vaccination was not necessary. Although the rate of seasonal influenza vaccination was high for those ≥65 years old, it was poor for those aged <65 years, despite vaccination being recommended for all adults with chronic medical conditions. Future education programs should target younger patient populations and health-care workers and focus on vaccine safety and efficacy in immunocompromised patients as well as in other high-risk groups.
